Large-size conveyor belts are often used on the sites which have not been put in order and hence a person does not approach, such as natural resources exploiting sites, so that the maintenance and checkup thereof are not accomplished sufficiently. In such a site, the elongation, wear, or temperature of a part of the conveyor belt sometimes increases abnormally, and thereby the conveyor belt is broken suddenly, by which work is interrupted inevitably. In this case, much time and cost are needed for restoration. Therefore, a means for detecting signs of accident in advance has been demanded strongly to perform preventive maintenance. However, no effective means is available, which poses a problem.
Also, in the case where objects to be conveyed have high temperatures, the rubber of conveyor belt is often deteriorated by the heat, and finally it is broken. Therefore, monitoring for preventing the internal temperature of conveyor belt from increasing to a predetermined temperature or higher has been demanded. Actually, however, although a method of measuring the surface temperature of conveyor belt is available, a means for measuring the internal temperature thereof is unavailable.
The present invention has been made in view of the above circumstances, and accordingly an object of the present invention is to provide a method and device for measuring elongation, wear, and internal temperature of a conveyor belt by detecting a magnetic field from a magnetic body embedded in the conveyor belt to catch signs of conveyor belt failure such as breakage, and also to provide a rubber magnet sheet serving as a magnetic body capable of being used while being embedded in the conveyor belt and a method of producing the rubber magnet sheet.